The invention relates to a membrane arrangement for electroacoustical transducers, in particular for headsets, in which one or more diaphragms lie in one plane when the transducers are in a use position, which plane extends in the immediate proximity of the user's external ear and preferably parallel to the tangential plane of the ear.
Headsets of this design are generally preferred at present. They are characterized by their good frequency response and small distortion factor. It was not yet possible however, despite all efforts, to eliminate another deficiency inherent in most headsets generally, namely the fact that direction and distance discernment by hearing with headsets usually does not conform to reality. Generally, a disturbing effect becomes noticeable in that the acoustic event does not become audible in front of the headset user as it should be, but more or less vaguely on the side, in the back, or raised out of the horizontal plane (elevation). This is attributable to the fact that when listening with headsets, the signals at the eardrum do not coincide with those perceived in actual live and free listening. Even slight deviations result in incorrect sound location fixing in the ear.
Essentially, the position of the diaphragm of a headset, relative to the natural direction of incidence of the sound waves is decisive, for when the headset is worn, the diaphragm is usually in a plane extending roughly parallel to the external ear so that the sound waves are radiated by the headset diaphragm approximately perpendicularly to the natural direction of incidence. To remedy this deficiency, it has already been suggested to arrange a diaphragm in such a way in the headset that the diaphragm is positioned, when in use, about perpendicular to the lateral direction of incidence, and in front of the user's external ear. Such an arrangement, however, has the disadvantage that the coupling space between diaphragm and ear becomes relatively large, which has an unfavorable effect at least on the efficiency of the headset and results in a loss in certain high frequency ranges.
The physical processes in sound transmission from a diaphragm to the ear with the interposition of a coupling space are expressed in the following theorem:
In the low frequency range from about 50 to 300 Hz the diaphragm mass and the restoring force due to the radial tension or the retention system furnishes a resonance which is increased to 1000 to 3000 Hz by the restoring force of the coupling space. Below this frequency range the diaphragm operates elastically inhibited, i.e. with constant amplitude at constant driving force, whereby frequency-dependent signals originate at the eardrum, as the external ear has influence in this range. Above this range, the amplitude of the diaphragm would drop, were it not for the directional radiation due to the size of the diaphragm. With a diaphragm area of 35 to 40 cm.sup.2 , a mass of about 0.015 g, and a small coupling space, into which the outer ear projects freely, the transition is gapless.